Burnham Series 5B - Manual (Page 50)

50
5. OP CONTROL SYSTEM – 5006B thru 5014B
The OP Control System utilizes an RM7890C
microprocessor based integrated burner control and
a Q179D Rectification Pilot (standing or continuous
burning pilot) to which has been added a Q309
thermocouple. The RM7890C Primary Control is a
non-programming, amplifying relay which, when used
with the Q179D Pilot, provides solid state electric
Flame Safeguard Protection during a “call for heat”
pilot failure. Main burner will shut down within 0.8
second and the RM7890C will lock out on safety
shutdown within 15 seconds. Should a pilot failure
occur during the “off” cycle, the thermocouple in the
Q179D pilot will cool and, within 45 to 90 seconds,
will cause the L62GB-3C Pilot Safety Switch to which
it is connected, to break the electrical circuit to the main
gas valve, as well as shut off the flow of gas to the pilot.
Thus, 100% shut-off is achieved.
a. LIGHTING INSTRUCTIONS
(1) Make sure Manual Main Shut-off Valve and
Pilot Valve have been off for at least five
minutes.
(2) Set Operating and Limit Controls to desired
setting.
(3) Turn on Main Electric Switch and Service
Switch.
(4) Turn Pilot Valve to Open Position.
(5) Depress button on L62GB-3C Pilot Safety
Switch and hold lighted match to pilot, holding
button in for one minute or until pilot remains
lighted after button is released.
(6) Press reset button on RM7890C relay.
(7) Open Manual Main Shut-off Valve – main
burner will light.
Proceed to Paragraph 15 - Minimum Input
Adjustments (for diaphragm “Lo-Hi-Lo” or
motorized type gas valves)
SEQUENCE OF OPERATION OP – see Fig. 46
b. NORMAL OPERATION – 5006B thru 5014B
(1) When the operating control calls for heat,
terminal #6 of RM7890C Relay is energized.
(2) A component check circuit in the RM7890C
Relay is activated which checks the electronic
network of the relay.
(3) Flame rod circuit of the RM7890C and Q179D
proves presence of pilot flame electronically.
(4) Terminal #9 is energized and supplies power to
the main gas valves.
(5) Main gas valves open and main burners are
lighted by pilot.
(6) When operating control is satisfied, terminals #6
and #9 are de-energized, Main Gas Valves close
and main burners are extinguished.
(7) The pilot continues to burn.
c. SAFETY SHUTDOWN
(1) SAFETY SWITCH CIRCUIT
If limit control, Low Water Cut-off or any
other electrical safety switch opens, power to
terminal #6 in Relay is interrupted thus de-
energizing terminal #9 in Relay. Main Gas
Valves are thus de-energized and main gas
burners are immediately extinguished. The
pilot will continue to burn. Normal operation
can be resumed when the cause of safety switch
malfunction is corrected. Make sure all manual
resets are activated where involved.
(2) PILOT FAILURE
(a) Flame rod supervision of pilot occurs only
during the operating cycle (call for heat) of
the operating control since the RM7890C
relay is only energized by the operating
control. If failure occurs during this period,
the main gas valves close and the main gas
burners are extinguished within 0.8 second.
After 15 seconds the relay will lock out on
safety shutdown.
(b) If the pilot failure occurs during the “off”
cycle of the operating control, the RM7890C
relay will not be powered thru terminal #6,
therefore, there is no electronic flame rod
supervision. This is due to the utilization of
a thermocouple in the Q179D modified pilot.
This thermocouple will cool in 45 to 90
seconds allowing the pilot line safety valve
to close. This shuts off the flow of gas to the
pilot. It is in this manner that 100% shut-off
is achieved. If the operating control calls for
heat during this period the RM7890C relay
will immediately sense “no flame” on pilot
and will lockout as described in paragraph
(a) above.
d. SHUTDOWN INSTRUCTIONS
(1) Close manual shut-off valve and pilot valve.
(2) Turn off main electric switch.
6. OP CONTROL SYSTEM 5015B thru 5026B
The 5015B thru 5026B boilers utilize two OP Control
Systems that are interconnected electrically thru all
operating and safety controls. Should any of the
aforementioned controls break the power supply circuit,
both OP control systems would be de-energized. The
succeeding paragraph describes the function and
operation of each OP Control System. Should a pilot
SecTiON iV - OPeRATiON (continued)